1. Field of the Invention
This invention relates to a transfer feeder for a forging press, which is provided on the forging press, and grasps forging workpieces, and feeds them from one step of a pressing process to another.
2. Related Art
One known apparatus for feeding workpieces from one step of a press-forging process to another is a transfer feeder having a pair of parallel feed bars. The two parallel feed bars have a plurality of opposed claw members for grasping the workpieces from opposite sides. The two feed bars are moved toward each other in parallel relation to each other to hold the workpieces therebetween, and then are moved upward to remove the workpieces from a lower die, and then are moved forward (or advanced) in an axial direction, and then are again moved downward, and then are moved away from each other, thus transferring the workpieces to the next step, and thereafter the two feed bars are returned respectively to their original positions. This operation is repeated.
One known conventional transfer feeder for enabling the above three-dimensional movement of the feed bars comprises servo motors, and feed screw mechanisms. For example, in an automatic transfer apparatus for a forging press, disclosed in Japanese Patent No. 2,560,970, an upwardly-downwardly-moving carriage is provided adjacent to one ends (rear ends) of feed bars, and is moved upward and downward by a lift-down servo motor and a feed screw, and an advance-return carriage (left-right moving carriage) and an advance-return servo motor are mounted on this upwardly-downwardly-moving carriage, and the advance-return carriage is advanced and returned, together with the feed bars by a feed screw, and the feed bars are supported on the advance-return carriage for movement toward and away from each other so as to effect a clamping-unclamping operation, and a clamping-unclamping servo motor is mounted on the advance-return carriage, and a feed screw, connected to this servo-motor, is threadedly engaged with the feed bars so as to move the feed bars toward and away from each other (that is, so as to effect the clamping-unclamping operation).
At a position adjacent to the other ends (front ends) of the feed bars, the lift-down movement and the clamping-unclamping movement are also effected by servo motors and feed screws of a similar construction described above for the above construction provided adjacent to the rear ends of the feed bars. However, any drive portion for effecting the advance-return movement is not provided adjacent to the front ends of the feed bars, and the end portions of the feed bars are inserted in a clamping-unclamping slider portion for sliding movement in an axial direction. The foregoing is an ordinary example of feed bar-moving mechanism comprising the servo motors and the feed screws, and the advance-return drive mechanism (including the feed screw) and the clamping-unclamping drive mechanisms (including the feed screws) are disposed at a level generally equal to the feed bars, and the feed bars are placed directly on the advance-return carriage, and besides a lower end portion of the lift-down feed screw extends downwardly through the lift-down carriage to a level lower than the feed bars, and is journalled in a suitable fixing frame.
As described above, in the conventional transfer feeder of the screw feed-type, the driving in the advance-return direction is effected only by one drive motor provided adjacent to one ends of the long feed bars, and the longer the feed bars, the larger the load on the motor, and besides it is difficult to achieve the high-speed, precise operation. Furthermore, the drive portions and the sliding movement-support portions are disposed at the same level of the feed bars, and in order to protect the sliding portions from scales, produced during a pressing operation, and lubricant for a dies, the sliding portions are covered with bellows. With this construction, however, the bellows are expanded and contracted while being exposed to the heat of the workpieces, the scales and the lubricant for the die, and therefore are liable to be deteriorated and damaged, so that the scales and so on intrude into the sliding portions. As a result, the sliding portions are subjected to premature wear, and cause vibrations, so that the feed bars can not be smoothly fed from one step to another, and therefore the inspection, repair and exchange must be effected frequently.
And besides, that portion of a transfer frame, at which the drive portions are provided, is disposed at a level lower than the feed bars, and this narrows a space for installing a charging-discharging device. Furthermore, cylinders for exchanging the feed bars are mounted on a press bed, and this is liable to cause various troubles, and besides when exchanging the feed bars, the feed bars are lifted, and this limits a space for a bolster.